The invention relates generally to land grid array (LGA) electronic modules and, more particularly, to features for locating the contact pads on an LGA module to the contacts in an LGA socket.
Competition and market demands have continued the trends toward faster, higher performance electrical systems, particularly with regard to computer systems. Along with the development of surface mount technology in the design of printed circuit boards, higher density electrical circuits, including higher density interconnect components have been developed to meet the increasing demand for higher performance electrical systems.
As is known in the art, surface mountable packaging allows for the connection of the package to pads on the surface of the circuit board rather than by contacts or pins soldered in plated holes extending through the circuit board. As used herein, the term “package” shall include at least a chip carrying module that is to be mounted to a circuit board. Surface mount technology allows for an increased component density on a circuit board, thereby saving space on the circuit board.
Area array socket connectors have evolved, along with surface mount technology, as one high density interconnect methodology. One application of surface mount technology, for example, is the land grid array (LGA) socket connector that is used with an LGA package. One major advantage of the LGA package is durability. The LGA package is not easily damaged during the installation or removal process or by handling in general. The LGA package includes an array of contact areas or pads on the mating side. The LGA socket includes an array of contacts and the circuit board includes a pad pattern or contact pad array that both correspond to the contact pad pattern on the LGA package.
When loaded into the socket, the LGA package registers on the interior side walls of the socket to locate the package with respect to the socket contacts. Because there is a nominal clearance between the socket walls and the LGA package, the contact pads on the package must contain sufficient surface areas to absorb the tolerances between the package and the socket, as well as any linear translation or wiping of the contacts across the contact pads upon deflection of the contacts when the package is loaded into the socket.
As the package becomes smaller and the contact pad and socket contact densities increase, the contact pad and contact spacing approach the combined manufacturing tolerances of the electronic package and the socket. Thus, maintaining proper registration of socket contacts with the contact pads becomes a challenge as package size decreases.